Re: [BUGS] BUG #2208: Low performance on select
On Wed, Jan 25, 2006 at 12:32:31PM +, Fahri CAKIROGLU wrote: > Consecutive selects from three different tables > causes low performance(about 1500 ms). > Same select count from two tables gives good performance(about 30 ms). This might be due to caching. When you query two tables all of the pages you need might be cached, but when you query a third table some of the pages from the other tables might be evicted from the cache. When you query one of those tables again the pages have to be fetched from disk. How big are the tables in question? > All searched keys are indexed and individual execution > of each query is very fast. Could you post the EXPLAIN ANALYZE output of each query? Have you tuned any of your postgresql.conf settings, in particular shared_buffers? How much memory do you have? -- Michael Fuhr ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
[BUGS] BUG #2208: Low performance on select
The following bug has been logged online: Bug reference: 2208 Logged by: Fahri CAKIROGLU Email address: [EMAIL PROTECTED] PostgreSQL version: 8.1 Operating system: windows nt 2000 Description:Low performance on select Details: Consecutive selects from three different tables causes low performance(about 1500 ms). Same select count from two tables gives good performance(about 30 ms). All searched keys are indexed and individual execution of each query is very fast. Slow query : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from invoice where invnum='1' order by inv limit 1; Query with good performance : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from orders where ordernum='2' order by ordernum limit 1; select * from customers where custnum='2' order by custnum limit 1; ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
